Phobos

. A close-up image of the Martian moon Phobos, taken from the Mars Global Surveyor. It shows the moon’s highly irregular shape and battered, cratered surface. The largest crater, Stickney (top left), is 10 kilometers in diameter, and about half the size of Phobos. This crater is named after Angeline Stickney (1830-1892), wife of Asaph Hall (1829-1907), who discovered the two Martian moons. Individual boulders can be seen near the rim of the crater, presumably ejected by the impact that formed Stickney. (Courtesy of NASA, JPL and Malin Space Science Systems.)